(1) Field of the Invention
The present invention generally relates to an apparatus, such as a communication equipment, ,having a plurality of plug-in packages detachably housed in a housing thereof.
(2) Description of Related Art
A communication equipment 1 generally has a structure as shown in FIG. 1. That is, a plurality of communication units 3-1, 3-2, 3-3 and 3-4 are mounted in a cabinet 2 so as to be stacked on each other. The communication units 3-1, 3-2, 3-3 and 3-4 are respectively provided with plug-in packages 5-1, 5-2, 5-3 and 5-4, in each of which plug-in packages an electric circuit for performing a predetermined function is provided. A plurality of plug-in packages are detachably housed in a housing (4-1, 4-2, 4-3 and 4-4) of each of the communication units. To change functions of the communication equipment 1, the plug-in packages must be replaced or additional plug-in packages must be added in at least one of the communication units 3-1, 3-2, 3-3 and 3-4. Thus, it is preferable that each of the plug-in packages be capable of being set in each of the communication units without pulling out the communication units from the cabinet. In addition, to prevent the height of the cabinet of the communication equipment from increasing, it is preferable that each of the communication units be as thin as possible.
FIG. 2 shows a conventional structure of a communication unit having a plurality of plug-in packages detachably housed in a housing thereof.
Referring to FIG. 2, a housing 4 of a communication unit 3 has a plurality of insertion openings 11 formed at predetermined intervals on a front surface 10 thereof. A back board 12 is mounted, in the housing 4, at a position close to the rear surface opposite to the front surface 10 of the housing 4. Each of plug-in packages 5 has a circuit board 16 and a plug-in connector 14 mounted at an end of the circuit board 16. A plurality of connectors 15 are fixed on the back board 12, each of the connectors 15 corresponding to one of the insertion openings 11. Each of the plug-in packages 5 is inserted into the housing 4 via one of the insertion openings 11 in a direction shown by an arrow in FIG. 2. Then, the plug-in connector 14 is connected with a corresponding one of the connectors 15. That is, the plug-in packages 5 are mounted in the housing 4 in a state where the plug-in connector 14 of each of the plug-in packages 5 is connected with a respective connector 15 fixed on the back board 12.
In the above conventional communication unit 3, the plug-in packages 5 are inserted into the housing 4 from the front surface 10 side of the housing 4. Thus, each of the plug-in packages 5 can be inserted into the housing 4 without pulling out the communication unit from the cabinet 2. However, as each of the communication units must be as thin as possible, the size of the back board 15 to which the plug-in packages 5 are electrically connected becomes small. Thus, the back board 12 cannot be used as a mother board on which a circuit for operating the plug-in packages 5 is formed. The circuit to be formed on the mother board is referred to as a common circuit. In each conventional communication unit, the common circuit is Separately formed on some of the plug-in packages. Thus, the number of plug-in packages to be housed in the housing of each communication unit increases, so that the size (the width) of the housing of each of the communication units increases.